As an operating valve assembly, there is a known one, in which a spool is slidably disposed in a spool bore provided in a valve body and switching flow of a pressurized fluid by shifting the spool, and in order to shift the spool, pressure receiving chambers are defined at left and right ends of the spool for driving the spool by supplying a pilot pressurized fluid.
The spool shifting type operating valve assembly is troublesome in assembling for necessity of connection of an electromagnetic proportioning pressure reduction valve for outputting the pilot pressurized fluid and the operating valve by a piping. Therefore, in place of the above-mentioned type of the operating valve assembly, there has been proposed an operating valve assembly, in which the electromagnetic proportioning pressure reduction valve is provided in a valve body.
In Japanese Unexamined Utility Model Publication (Kokai) No. Heisei 3-30678, there is disclosed an operating valve assembly, in which a pressure reduction valve receptacle bore 3 is formed in a valve body 2 having the spool bore with a spool 1 slidingly disposed therein, a pressure reduction valve 4 is slidingly disposed in the pressure reduction valve receptacle bore 3, and a solenoid 5 for driving the pressure reduction valve 4 is provided at the end face of the valve body to form the electromagnetic proportioning pressure reduction valve 6. It should be noted that the reference numeral 8 denote pressure receiving chambers at left and right end sides of the spool 1, as shown in FIG. 1.
On the other hand, Japanese Unexamined Utility Model Publication No. Heisei 1-29581, there is disclosed an operating valve assembly, in which the pressure reduction valve 4 is slidably disposed in a main body 7, and the solenoid 5 for driving the pressure reduction valve 4 is mounted on the main body 7 to form the electromagnetic proportioning pressure reduction valve 6, and the main body 7 is mounted at a spring chamber side of the valve body 2, as shown in FIG. 2.
However, in the case of the former operating valve assembly, it becomes necessary to form a fluid conduit 9 in the valve body 2 for communicating the pressure reduction valve receptacle bore 3, an inlet port 3a for pilot pressure, a tank port 3b and the pressure receiving chambers 8 with the output side. Therefore, the structure of the valve body 2 becomes specific for the operating valve assembly with the electromagnetic proportioning pressure reduction valve. Thus, the valve body 2 cannot be common to the main body for the typical ordinary operating valve assembly.
On the other hand, in the case of later operating valve assembly, since two electromagnetic proportioning pressure reduction valves 6 are mounted at one side of the valve body 2, a plane view configuration of the overall operating valve assembly (configuration in a plane perpendicular to the axial center of the spool 1) becomes large. Thus, a spatial difficulty is encountered in installation of an auxiliary valve. On the other hand, when the auxiliary valve is installed, the plane configuration becomes very large to require large installation area.
Therefore, it is an object of the present invention to provide an operating valve assembly with an electromagnetic proportioning pressure reduction valve which does not require to provide an output circuit of the electromagnetic proportioning pressure reduction valve in a valve body, permits the valve body to be common to the valve body of the ordinary operating valve assembly, thus can form the operating valve assembly with the electromagnetic proportioning pressure reduction valve with one valve body, can be the ordinary operating valve assembly, can be compact in plane configuration to facilitate installation of an auxiliary valve, and can be installed in a small area even when the auxiliary valve is mounted.